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From "Laljo John Pullokkaran (JIRA)" <>
Subject [jira] [Created] (HIVE-6540) Support Multi Column Stats
Date Mon, 03 Mar 2014 21:48:20 GMT
Laljo John Pullokkaran created HIVE-6540:

             Summary: Support Multi Column Stats
                 Key: HIVE-6540
             Project: Hive
          Issue Type: Improvement
            Reporter: Laljo John Pullokkaran
            Assignee: Laljo John Pullokkaran

For Joins involving compound predicates, multi column stats can be used to accurately compute
the NDV.

Objective is to compute NDV of more than one columns.

Compute NDV of (x,y,z).

R1 IJ R2 on R1.x=R2.x and R1.y=R2.y and R1.z=R2.z can use max(NDV(R1.x, R1.y, R1.z), NDV(R2.x,
R2.y, R2.z)) for Join NDV (& hence selectivity).

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